Different types of cell rearrangement take place during gastrulation, organogenesis, and cell migration. Oriented rearrangement of cells within a simple epithelium is essential for elongation of a number of different types of cell sheets and tubes. Since it elongates without either cell proliferation or apoptosis, the Drosophila hindgut is particularly suitable for genetic analysis of cell rearrangement within an epithelium. The Lengyel lab has defined a sequence of spatially localized (patterned) gene activity required for this oriented cell rearrangement: a hierarchy of transcriptional regulators (drm-lin-bowl) causes expression of the Drosophila JAK/STAT ligand Unpaired (upd) at the anterior of the hindgut (small intestine); this results in a gradient of STAT protein along the anteroposterior (elongating) axis. Our testable hypothesis is that cell signaling from the small intestine is required to orient and promote cell rearrangement. My proposed research will investigate this hypothesis by both genetic and morphogenetic analysis. Further, I will be involved in a large scale screen of embryos from lethal lines to identify other novel genes controlling oriented hindgut cell morphogenesis and rearrangement in Drosophila. [unreadable] [unreadable]